α9α10 nicotinic acetylcholine receptors regulate murine bone marrow granulocyte functions.

Polymorphonuclear neutrophilic granulocytes (PMNs) are extremely important in defense of the organism against infections and in inflammatory processes including neuroinflammation and pain sensation. Different subtypes of nicotinic acetylcholine receptors (nAChRs) are involved in modulation of PMN activities. Earlier we determined expression of α2-7, α9, β3, β4 subunits and regulatory role of α7 and α3β2 nAChR subtypes in functions of inflammatory PMNs.

Snake C-type lectin-like proteins inhibit nicotinic acetylcholine receptors.

Venoms of viperid snakes affect mostly hemostasis, while C-type lectin-like proteins (CTLPs), one of the main components of viperid venoms, act as anticoagulants, procoagulants, or agonists/antagonists of platelet activation. However, we have shown earlier that CTLPs from the saw-scaled viper , called emunarecins EM1 and EM2, were able to inhibit nicotinic acetylcholine receptors (nAChRs) in neurons of a pond snail (). Here we analysed the structure of the emunarecins by mass spectrometry and report that EM1 and EM2 inhibit fluorescent α-bungarotoxin binding to both muscle-type nAChRs from and human neuronal α7 nAChRs.

PNU-120596, a positive allosteric modulator of mammalian α7 nicotinic acetylcholine receptor, is a negative modulator of ligand-gated chloride-selective channels of the gastropod Lymnaea stagnalis.

Excitatory α7 neuronal nicotinic receptors (nAChR) are widely expressed in the central and peripheral nervous and immune systems and are important for learning, memory, and immune response regulation. Specific α7 nAChR ligands, including positive allosteric modulators are promising to treat cognitive disorders, inflammatory processes, and pain. One of them, PNU-120596, highly increased the neuron response to α7 agonists and retarded desensitization, showing selectivity for α7 as compared to heteromeric nAChRs, but was not examined at the inhibitory ligand-gated channels.

Pancreatic and snake venom presynaptically active phospholipases A2 inhibit nicotinic acetylcholine receptors.

Phospholipases A2 (PLA2s) are enzymes found throughout the animal kingdom. They hydrolyze phospholipids in the sn-2 position producing lysophospholipids and unsaturated fatty acids, agents that can damage membranes. PLA2s from snake venoms have numerous toxic effects, not all of which can be explained by phospholipid hydrolysis, and each enzyme has a specific effect.

Peptides from puff adder Bitis arietans venom, novel inhibitors of nicotinic acetylcholine receptors.

Phospholipase A (named bitanarin) possessing capability to block nicotinic acetylcholine receptors (nAChRs) was isolated earlier (Vulfius et al., 2011) from puff adder Bitis arietans venom. Further studies indicated that low molecular weight fractions of puff adder venom inhibit nAChRs as well.

Nicotinic receptor involvement in regulation of functions of mouse neutrophils from inflammatory site.

Participation of nicotinic acetylcholine receptors (nAChRs) in functioning of polymorphonuclear neutrophils (PMNs) isolated from inflammatory site of mice and expression of different nAChR subunits were studied. Nicotine and acetylcholine (ACh) modified respiratory burst induced by a chemotactic peptide N-formyl-MLF in neutrophils of male (but not female) mice. Antagonists of nAChRs α-cobratoxin (αCTX), α-conotoxins MII and [A10L]PnIA at concentrations of 0.

Natural compounds interacting with nicotinic acetylcholine receptors: from low-molecular weight ones to peptides and proteins.

Nicotinic acetylcholine receptors (nAChRs) fulfill a variety of functions making identification and analysis of nAChR subtypes a challenging task. Traditional instruments for nAChR research are d-tubocurarine, snake venom protein α-bungarotoxin (α-Bgt), and α-conotoxins, neurotoxic peptides from Conus snails. Various new compounds of different structural classes also interacting with nAChRs have been recently identified.

Inhibition of nicotinic acetylcholine receptors, a novel facet in the pleiotropic activities of snake venom phospholipases A2.

Phospholipases A2 represent the most abundant family of snake venom proteins. They manifest an array of biological activities, which is constantly expanding. We have recently shown that a protein bitanarin, isolated from the venom of the puff adder Bitis arietans and possessing high phospholipolytic activity, interacts with different types of nicotinic acetylcholine receptors and with the acetylcholine-binding protein.

An unusual phospholipase A₂ from puff adder Bitis arietans venom--a novel blocker of nicotinic acetylcholine receptors.

The venoms of snakes from Viperidae family mainly influence the function of various blood components. However, the published data indicate that these venoms contain also neuroactive components, the most studied being neurotoxic phospholipases A₂ (PLA₂s). Earlier we have shown (Gorbacheva et al.

Alpha-conotoxin analogs with enhanced affinity for nicotinic receptors and acetylcholine-binding proteins.

Alpha-conotoxins, neurotoxic peptides from poisonous Conus marine snails, can be subdivided into several groups targeting distinct subtypes of nicotinic acetylcholine receptors (nAChRs). Such alpha-conotoxins as, for example, GI, MI, or SIA potently block muscle-type nAChRs from muscles and from the electric organ of Torpedo ray, whereas others target distinct neuronal nAChRs: alpha-conotoxins ImI and PnIB block pentaoligomeric alpha7 nAChRs, and alpha-conotoxins MII or PnIA inhibit heteromeric nAChRs made of combinations of alpha3 or alpha6 subunits with beta2 subunit. alpha-Conotoxins interact with N-terminal extracellular ligand-binding domains of nAChRs and are indispensable tools for distinguishing various subtypes of AChRs at normal and pathological states.

Alpha-conotoxin analogs with additional positive charge show increased selectivity towards Torpedo californica and some neuronal subtypes of nicotinic acetylcholine receptors.

Alpha-conotoxins from Conus snails are indispensable tools for distinguishing various subtypes of nicotinic acetylcholine receptors (nAChRs), and synthesis of alpha-conotoxin analogs may yield novel antagonists of higher potency and selectivity. We incorporated additional positive charges into alpha-conotoxins and analyzed their binding to nAChRs. Introduction of Arg or Lys residues instead of Ser12 in alpha-conotoxins GI and SI, or D12K substitution in alpha-conotoxin SIA increased the affinity for both the high- and low-affinity sites in membrane-bound Torpedo californica nAChR.

Diversity of nicotinic receptors mediating Cl- current in Lymnaea neurons distinguished with specific agonists and antagonist.

Diversity of nicotinic acetylcholine receptors (nAChRs) mediating Cl- current in voltage-clamped identifiable Lymnaea stagnalis neurons was studied using acetylcholine (ACh), three agonists and alpha-conotoxin ImI (ImI). Cytisine, nicotine, and choline, full agonists at alpha7 subunit-containing nAChRs of vertebrates, were found to evoke at saturating concentration 84-92% of the maximal current elicited by ACh. ImI, known to block selectively alpha7 and alpha9 nAChRs, markedly diminished the responses to ACh.

Nicotinic receptors in Lymnaea stagnalis neurons are blocked by alpha-neurotoxins from cobra venoms.

The influence of cobra neurotoxins on the Cl-dependent responses to acetylcholine (ACh) of Lymnaea neurons was studied by the voltage-clamp technique. It was found that a short chain neurotoxin II (NT II), a long chain cobratoxin (CTX) and weak neurotoxin (WTX) diminished the ACh-induced currents, the block being concentration-dependent and competitive. The IC(50) values of 130 nM for CTX, 11 microM for NT II, and 67 microM for WTX were determined.

Independence of and interactions between GABA-, glutamate-, and acetylcholine-activated Cl conductances in Aplysia neurons.

In certain Aplysia neurons, glutamate, GABA, and acetylcholine (ACh) all elicit desensitizing Cl-dependent responses. This fact and the finding that the glutamate and GABA responses "cross-desensitize" led to the suggestion (Swann and Carpenter, 1975; King and Carpenter, 1987) that the responses to these transmitters were mediated by the same receptor-channel complex. This hypothesis is incompatible with the demonstration given here that the GABA- and glutamate-gated channels are clearly distinct; the GABA channel, but not the glutamate channel, shows outward rectification (Matsumoto, 1982; King and Carpenter, 1987, 1989) and is selectively blocked by intracellular sulfate.

Intracellular Ca2+ modulates Cl- current evoked by acetylcholine in Lymnaea neurons.

The influence of voltage-gated Ca2+ current (ICa) on Cl current (ICl) initiated by nicotinic receptors (AChRs) in dialysed voltage-clamped Lymnaea neurons was studied. Depolarising steps applied before or during ACh application decreased ICl transiently and slowed down both the rising phase and decay of ICl. The effect of ICa depended on the interval between ICa and ICl; it was prevented by intracellular buffering with BAPTA or Ca2+ channel blocking with Ni2+.

Intracellular ATP modulates desensitization of acetylcholine receptors controlling chloride current in Lymnaea neurons.

Chloride current activated by nicotinic acetylcholine receptors (AChR) was examined in dialysed voltage-clamp neurons of Lymnaea stagnalis. Fast superfusion of acetylcholine (ACh) evoked an inward current rapidly rising to a peak followed by a decline due to desensitization. When adenosine triphosphate with Mg2+ (MgATP, 2-10 mM) was added intracellularly the peak of the ACh-induced current was increased and its decay was slowed down.

Intracellular ATP modifies the voltage dependence of the fast transient outward K+ current in Lymnaea stagnalis neurones.

1. The action of intracellular ATP on the fast transient outward K+ current (A-current) was studied in dialysed voltage-clamped Lymnaea stagnalis neurones. 2.

Modulation of nicotinic acetylcholine receptors by intracellular calcium and cyclic AMP in Lymnaea stagnalis neurones.

Acetylcholine (ACh)-receptor ion channels were investigated under the modulatory action of calcium and cyclic AMP in completely isolated Lymnaea stagnalis neurones using the noise analysis technique. Elevation of the intracellular Ca2+ concentration in dialyzed neurones produced a reduction in the amplitude of ACh induced current accompanied by slight decrease in the mean channel open time and a simultaneous 1.5-fold increase in mean channel conductance.

Intracellular Mg2+ modulates the A-current and its blockage by catechol in isolated Lymnaea neurons.

The effects of intracellular Mg2+ (2-8 mM) upon the transient outward current (the A-current) under normal conditions and under catechol-induced blockage were studied in molluscan neurons by using the voltage-clamp and intracellular dialysis techniques. Identified giant Lymnaea stagnalis L. neurons were investigated at room temperature (20-22 degrees C).

Depression of neuron responses to acetylcholine by combined application of norepinephrine and substrates of the tricarboxylic acid cycle.

The possible relationship between the function of nicotinic acetylcholine receptors in Lymnaea stagnalis neurons and energy metabolism was studied. Oxidative phosphorylation was activated by treatment of neurons with substrates of the tricarboxylic acid cycle and norepinephrine. Transmembrane currents induced by acetylcholine in isolated neurons were measured by voltage clamp.

Two-component desensitization of nicotinic receptors induced by acetylcholine agonists in Lymnaea stagnalis neurones.

The kinetics of desensitization induced by different agonists of acetylcholine (ACh) as well as the kinetics of recovery from densensitization, have been studied using the voltage-clamp technique in isolated, identified Lymnaea stagnalis neurones. Desensitization follows the sum of two exponentials: one fast and one slow. The time constant of the fast desensitization component (tau Ids) under ACh application is in the range of seconds at room temperature (18-23 degrees C).

Interaction between acetylcholine and other agonists at cholinoreceptive membrane of mollusc neurons.

The effect of pretreatment with agonists of various chemical structure on acetylcholine action at isolated Limnaea stagnalis neurones was studied. Threshold concentrations of monoquaternary agonists or dicholinic ester of adipinic acid increase and inhibit the responses to low and high acetylcholine concentrations respectively. In contrast, suberyldicholine and compound IEM-1054 (containing two charged ammonium groups in a molecule with an internitrogen distance of 2.